This invention relates generally to equipment supports, and more particularly, to portable equipment utilized in conjunction with motion picture film or video cameras.
In employing motion picture film cameras or video cameras to capture a sequence of images, it is extremely important to maintain the camera which is used in as stable a position as possible in order to obtain a high quality result. This is important in eliminating the effects of undesirable camera motion while in use. This is particularly desirable when employing such cameras under conditions wherein it is necessary or desirable for the camera to be mobile, or subjected to movement to acquire the images which are desired.
In order to overcome these problems, and to reduce the expense encountered in producing motion picture films and video productions, the "Steadicam.RTM." portable camera stabilizing device was developed. Using this device, which has become a de-facto standard in the industry, high quality results have been obtainable in a variety of circumstances. This is so even when the camera operator walks or runs with the camera because of the attendant increase in stability, particularly in stabilizing quick angular deviations along the axes of pan, tilt and roll, which previously could not be adequately controlled.
Further detail regarding the "Steadicam.RTM." camera stabilizing device may be found with reference to U.S. Pat. No. Re. 32,213 (formerly U.S. Pat. No. 4,017,168); U.S. Pat. No. 4,156,512; and 4,474,439. A key component of this device is the so-called "arm" which serves as the interface between the frame which supports the camera and its ancillary components (e.g., battery packs, view finders, remote control equipment, etc.) and the body harness which is worn by the camera operator. Further detail regarding this support arm may be found with reference to U.S. Pat. Nos. 4,208,028 and 4,394,075.
The support arm disclosed in U.S. Pat. Nos. 4,208,028 and 4,394,075 is generally comprised of a pair of substantially friction-free arm sections which are rotatably and pivotally interconnected at a hinge bracket. Each arm section is formed as a parallelogram, and is provided with segmented springs which are designed to apply a constant force to compensate for the weight applied to the end of the support arm. As a result of this, the weight carried by the support arm is spatially decoupled from the body mounting to increase isolation of the weight from the operator as well as the camera support itself.
A principal design feature of the support arm, which is critical to proper functioning of the "Steadicam.RTM." camera stabilizing device, is the ability of the support arm to support the fixed weight of the overall system from its lowest to its highest point of articulation with a relatively constant amount of positive "buoyancy". This ability is generally referred to as "iso-elasticity", and the maintenance of such iso-elasticity is quite critical in ensuring effective operations of the "Steadicam.RTM." camera stabilizing device.
The mechanical principles and geometry of the support arm disclosed in U.S. Pat. Nos. 4,208,028 and 4,394,075 are perfectly valid for a variety of different types of cameras. However, a particular design was only found to be valid for a particular type of camera, primarily due to weight considerations, and was found not to be readily adaptable to different types of cameras. Nevertheless, in practice, use of the "Steadicam.RTM." camera stabilizing device has generally come to require its use in conjunction with different types of cameras. This is because practicalities such as space availability and cost considerations tend to prevent the dedication of different camera stabilizing devices to the different cameras necessary for a particular production. Consequently, means for adjusting the support capabilities of the arm of the "Steadicam.RTM." camera stabilizing device have become an ever-increasing consideration.
Responding to this need, adjustability has been provided for by altering the tension of the springs used in conjunction with the arm sections of the support arm in order to increase or decrease the load characteristics of the resulting spring set. While this allowed cameras of different weight to be supported by the arm, it was found that the desired positive buoyancy for the arm was only valid in one position of its vertical articulation. In other words, the feature of isoelasticity was lost. What is more, the adjustments required for altering spring tension were significant and time consuming, and therefore to be avoided.
Also to consider is that in some cases, it was found that perfect iso-elasticity is not ideal since it is desirable for the support arm to have a slight tendency to float at a desired height, with a minimal but consistent force required to fully raise or lower the support arm when in use. In such cases, an ability to adjust the degree of iso-elasticity of the support arm would be useful to conform to the requirements of different kinds of shooting (e.g., vehicle shots or the like, which require a firmer "ride" of the suspended equipment).
In practice it was found that while a given support arm would exhibit iso-elasticity when tensioned to the precise design parameters for a given spring configuration, an adjustment of the degree of iso-elasticity was not possible. At times, the camera stabilizing device tended toward an uncontrollable, "hard ride" when the springs were detensioned (e.g., to accommodate lighter cameras). Even for properly established, iso-elastic spring tensions, difficulties were encountered. Slight variations in the geometry of the support arm while under load sometimes caused the arm to be, in effect, overly iso-elastic. This led to an undesirable tendency of the support arm to lift more strongly at its highest excursion, and less strongly at its lowest. In such cases, the support arm required bumpers to restrict its highest and lowest travel in order to prevent the support arm from locking up at these extreme positions.